This invention relates to a battery having a plurality of electrical storage cells, and, more particularly, to such a battery having improved mechanical stability against vibrations.
Rechargeable cells o r batteries are electrochemical devices for storing and retaining an electrical charge and later delivering that charge as useful power. A familiar example of the rechargeable cell is the nickel-cadmium cell used in various portable electronic devices such as cameras and radios. Another type of cell having a greater storage capacity for it s weight is the nickel-hydrogen cell. The nickel-hydrogen cell is used in spacecraft such as satellites to store power generated by solar cell s when the spacecraft is in sunlight, and discharged to supply power when the spacecraft is in darkness.
A battery of this type has a plurality of individual electrochemical storage cells. Each of the storage cells utilizes a nickel positive electrode, a negative electrode, and an electrolyte as the basic charge-storing element. For example, the nickel-hydrogen battery includes a series of active storage cells, each storage cell having a nickel/nickel oxide positive electrode (termed a "nickel electrode"), a hydrogen negative electrode, a separator between the electrodes, and an electrolyte such as a potassium hydroxide solution. A stack of the storage cells is packaged within a pressure vessel that contains the stack, the electrolyte, the hydrogen gas evolved and consumed during the charge/discharge cycle of the cell, and gas screens between the storage cells to permit the hydrogen gas to flow to and from the electrodes.
The stacked configuration of storage cells is subjected to external loads or shocks during launch of a spacecraft containing the battery. The stack has a natural vibration frequency that may be excited by these loadings. If the vibrations are sufficiently severe, the battery may be damaged and rendered partially or fully inoperable.
Various design approaches have been utilized that could minimize the possibility that a battery can be damaged. The battery may be reinforced to resist loadings, but such reinforcement adds weight to the battery that reduces its specific storage performance. In another approach, the battery stack has been divided in half, and the two half stacks are separately supported from a central support within the battery container. The present inventors have recognized that this suggested design has drawbacks, however, because the two half stacks are dynamically coupled and supported in a cantilevered fashion that may readily vibrate. Dissipation of thermal energy is also inefficient in this approach.
There s a need for an improved battery design to resist vibration-induced damage. The present invention fulfills this need, and further provides related advantages.